1. Field of the Invention
The present invention relates to a method and apparatus for recording data on an optical recording medium, and more particularly, to an improved recording method and apparatus adapted with a high density and a high recording speed of an optical disc.
2. Description of the Related Art
Recording data on an optical disc means to form marks and spaces on a spatial track formed on the optical disc. A mark is formed as a pit in a read-only disc such as a Compact Disc-Read Only Memory (CD-ROM) and a Digital Versatile Disc-Read Only Memory (DVD-ROM). In a recordable disc such as a CD-R/RW and a DVD-R/RW/RAM, the mark is formed by radiating a laser signal on a phase-change recording film, which changes into a crystal phase or an amorphous phase according to a temperature level, or a recording film coated with an organic pigment having a light transmissivity that changes according to the temperature level.
In terms of signal detection, methods to record data on the optical disc can be divided into a mark edge recording method and a mark position recording method. According to the mark position recording method, a polarity of a detected radio frequency (RF) signal changes into an opposite polarity at a location at which the mark is recorded. According to the mark edge recording method, the polarity of the detected RF signal changes into the opposite polarity at both edges of the mark. Therefore, recording the edges of a mark is an important factor to improve a quality of a reproducing signal.
However, in the optical disc coated with the phase-change recording film, a shape of a trailing edge of the mark that is recorded, according to a conventional recording method, varies with a length of the mark or an interval between marks, i.e., a space therebetween. That is, when an interval between a trailing edge of a mark and a leading edge of the mark is large, recording and reproducing characteristics degrade. When a recording mark is relatively long, the characteristics degrade more due to thermal accumulation, which is referred to as a tear drop. The thermal accumulation influences very much a jitter characteristic of a recording signal.
In the meantime, recording the data on the optical disc is influenced by a recording speed. Nowadays, CD-Rs supporting 24× speed have appeared on the market, and DVDs supporting 4× speed are expected soon.
An increase of the recording speed means that a time taken to form marks having the same length is shortened inversely proportional to the recording speed. Accordingly, a high-power laser diode or an improved recording pulse is required.
Recording the data on the optical disc is also influenced by a high recording density. Research efforts on this topic has led to a 4.7 Gbyte HD-DVD (in case of a single layer and single surface), and 23 Gbyte HD-DVD (in case of a single layer and single surface) and a 50 Gbyte HD-DVD has also been investigated. An increase of the recording density means that a track pitch is narrowed or a minimum mark length is shortened. As a result, cross erase occurs or interference between marks increases. Consequently, a more elaborate recording control is desired.